1. Field of the Invention
This invention relates to a magnetic recording device, a magnetic recording method, and a magnetic recording medium for a shingle write scheme.
2. Description of the Related Art
In recent years, an improvement in performance of a magnetic write head has been demanded, due to an increase in an areal recording density of a magnetic recording medium (hereinafter, referred to as a “recording medium”) typified by a hard disk. In response thereto, in substitution for a longitudinal magnetic recording scheme in which a direction of a signal magnetic field is set to an in-plane direction of a recording medium, attention is attracted, as a recording scheme of the magnetic write head, to a perpendicular magnetic recording scheme in which the direction of the signal magnetic field is set to a direction intersecting the plane thereof. The reason is that there are such advantages that a linear recording density improves, and a recording medium on which recording has been already performed is less susceptible to thermal fluctuation.
A magnetic write head of the perpendicular magnetic recording scheme (hereinafter, referred to as a “perpendicular magnetic write head”) is provided with a thin-film coil for generating a magnetic flux, and a main magnetic-pole layer for leading the magnetic flux generated in the thin-film coil to a magnetic recording medium. The main magnetic-pole layer includes a tip portion (a magnetic pole) having a fine width, which generates a magnetic field for recording (a recording magnetic field).
As for a configuration of the perpendicular magnetic write head, a provision of a side shield layer on both sides of a magnetic pole in a write-track width direction with a gap inbetween has been under consideration, in order to address a higher recording density while suppressing a spread of the recording magnetic field (for example, see Japanese Unexamined Patent Application Publication No. 2004-326990, No. 2004-022004, and No. 2005-310363).
In these days, there has been a trend of ever increasing demand for further improvement in the areal recording density of the magnetic recording medium. Under such circumstances, a new magnetic recording scheme called a shingle write scheme (Shingle Write scheme) has been proposed (for example, see Japanese Unexamined Patent Application Publication No. 2006-294162, No. 2007-73138, and No. 2010-40113). The shingle write scheme writes a part of a magnetic write track in an overlapped fashion (performs writing of a subsequent magnetic write track in such a manner as to overwrite a part of a region of a previously-written magnetic write track). This allows a width of a magnetic write track obtained eventually to be narrower than a width of a trailing edge of a magnetic pole, thus improving the areal recording density of the magnetic recording medium. However, due to having such a feature, it is physically impossible, except for a final write track, to perform a data rewriting process only on an optional unit recording region. Consequently, a recording process has to be performed on all of the magnetic write tracks including even the magnetic write track which, under normal circumstances, does not need to be rewritten. As a result, the processing time required for the data rewriting process increases as compared with a normal recording scheme. Therefore, a method has been proposed, which shortens the processing time for rewriting by providing a plurality of data recording blocks on a magnetic write track, and performing the data rewriting process on each recording block basis. In this case, the plurality of data recording blocks are arranged so as not to be overlapped one another.
Incidentally, an erase band occurs in regions on both side edges of a magnetic write track, over which a magnetic pole of a magnetic write head has passed and a magnetic data has been recorded (a recording region in which a magnetization direction is disordered), due to a phenomenon referred to as a so-called writing exudation. In particular, a relatively large erase band occurs when an angle of inclination (a skew angle) of a main magnetic pole relative to a tangential direction (a direction of rotation of a magnetic disk, or a direction of movement of the main magnetic pole) of the write track is large. Thus, when providing the plurality of data recording blocks on the magnetic disk, it is necessary to ensure a clearance region to an extent in which they do not interfere mutually at the time of the data rewriting process. However, although errors such as erroneous erasure and erroneous writing of data can be avoided, the ensuring of wide clearance region, as a matter of course, incurs a decrease in the areal recording density of the magnetic recording medium.
In view of such circumstances, a magnetic recording device, a magnetic recording method, and a magnetic recording medium for a shingle write scheme, capable of shortening the processing time without involving a generation of error at the time of data rewriting process, and yet adaptable to high-density recording, are strongly desired.